In a peristaltic pump, the pumped fluid contacts only the bore of a tube, thereby eliminating the risk of the pump contaminating the fluid. Peristaltic pumps are therefore often used to pump sterilized fluids, and thus find applications particularly in the biopharmaceutical industry.
In a peristaltic pump, a compressible tube is squeezed between a roller and a track on an arc of a circle, creating a seal at the point of contact. As the roller advances along the tube, the seal also advances. After the roller has passed, the tube returns to its original shape, creating a partial vacuum which is filled by fluid drawn from the suction port.
Before the roller reaches the end of the track, a second roller compresses the tube at the start of the track, isolating a packet of fluid between the compression points. As the first roller leaves the track, the second continues to advance, expelling the packet of fluid through the pump's discharge port. At the same time, a new partial vacuum is created behind the second roller into which more fluid is drawn from the suction port.
The fluid discharged by peristaltic pumps exhibits a characteristic pulsation in pressure generated by the pumping method. Some applications are sensitive to pulsating fluid flow. and so steps may be taken to reduce the pulsation. For example, the pulsation amplitude may be reduced using two channels which are out of phase from one another and are manifolded to one another on the discharge side of the pump. This may be achieved using a rotor with two offset sections or a pair of offset tracks. This is known to deliver a net reduced pulse amplitude and increased pulse frequency but only at a system pressure of up to 2 bar. With system pressures of 2-4 bar, the pulse amplitude grows significantly, and is very difficult to control to less than 0.5 bar without additional system pulsation damping devices.
It is therefore desired to provide a peristaltic pump which exhibits reduced pulsation characteristics.